Mayor Thomas M. Menino has given a thumbs down to a $343 million plan by the Massachusetts Eye and Ear Infirmary to build a 10-story building on air rights over the Charles Street Extension and a 1,000 car garage under Storrow Drive.

“I’m against it right now,” Menino told the Boston Business Journal. “Where’s the money coming from? How are they going to change the configuration of the roadway? They want to do air rights over Charles Street. How do you do that? It’s a historical district.”

On Wednesday night, at press time, hospital staff was scheduled to hold a meeting for the Beacon Hill neighborhood to detail its planned expansion. Under the proposal, the Harvard Medical School-affiliated teaching hospital and world-renowned research center would replace a pair of surface parking lots it leases from the commonwealth with a three-acre park and build an underground four-level parking garage for 1,065 spaces at a cost of $173 million. The second aspect of the project would include construction of an 180,000-square-foot facility above the Charles Street Extension near the Liberty Hotel with an estimated cost of $170 million. Under the proposal, the new building would extend out above the proposed park and garage, giving patients direct access to the hospital.

Jennifer Street, vice president of communication and planning, said the hospital serves 260,000 patients annually and that number is expected to grow as baby boomers reach a point where they will need vision and other kinds of care. She said the 530,000-square-foot space they own in three building is insufficient to meet the needs of a growing patient population. “We are on a very constrained campus and we’re out of space,” she said.

Last year, the hospital filed a plan with the Boston Redevelopment Authority for a $150 million expansion. At the time, the hospital wanted to build a 90,000-square-foot research facility at 325 Cambridge St., replacing three outdated buildings in front of Mass. General’s Yawkey Center for Outpatient Care. But Street said the modest plan was scrapped when the community reacted saying they were not thinking boldly enough. She also noted that the 327 spaces they lease from the Department of Conservation and Recreation at an annual cost of $120,000 is insufficient. “That concept did not try to solve our parking problem, so we went back to the drawing board,” she said.

Construction of the underground parking garage would require a realignment of Storrow Drive as well as access ramps at Charles Circle. Street said the hospital would ask the state to pay for about $30 million of the $170 million cost of the project.

Stephen Young, president of the Beacon Hill Civic Association, said while residents would welcome transformation of parking lots into green space, the neighborhood is worried that the addition of a 1,000 car garage would wreak havoc on an already congested part of the city.

“It would be a real plus to turn parking lots into park land,” he said. “But they’re talking about increasing parking by 700 vehicles. We are concerned about the impact on the Beacon Hill neighborhood, Cambridge Street and Charles Circle which is already jammed. Reconstruction of the Longfellow Bridge is coming and that would add to the problem.”

Still, Young said, the neighborhood is willing to listen. “We are not ready to be all excited or all negative before we’ve even had the plan introduced to us,” he said.